2 letters:
dp, tc, tt

3 letters:
eas, far, fdr, prc, see

4 letters:
base, camp, dprk, elam, eyre, firm, folk, glut, gray, home, land, open, oran, oslo, poor, port, rape, reel, rock, ruin, siam, ussr, visa, wold

5 letters:
abuja, acres, adapt, alien, apart, benin, brief, china, dacha, dwell, erupt, exile, expel, frost, harsh, india, junta, katar, lodge, loyal, march, nepal, niger, oiled, qatar, rearm, rural, scour, silva, sylva, throe, tibet, trail, villa, visit, weald

6 letters:
abroad, armory, banish, barrio, belize, betray, bharat, brasil, brazil, caller, canaan, canton, citify, colony, consul, cyprus, defect, depict, deport, desert, drench, emigre, estate, export, father, fealty, folksy, france, govern, import, nation, people, rapine, recall, reform, regent, reject, russia, rustic, simple, source, soviet, spread, squire, strafe, sultan, sunday, system, thibet, thrace, tirana, townee, upland, zurich

7 letters:
armoury, arsenal, bahamas, bahrain, bahrein, bucolic, bushman, chateau, colchis, comoros, costume, criollo, crooked, dahomey, defence, defense, deliver, demesne, dissent, diverse, emigree, entrant, eritrea, etruria, exclude, galatia, holland, hostile, jamaica, kingdom, landler, laputan, lindsay, lowland, midland, migrant, migrate, nigeria, outback, outgoer, parthia, patriot, peasant, phrygia, present, rambler, readmit, reshape, reunify, reunite, romance, settler, sitsang, sleeper, suspend, traitor, trekker, trouper, viceroy, walk-in, winding

8 letters:
adoptive, agrestic, airforce, american, arcadian, autobahn, aviation, bithynia, blowback, cabotage, catalyst, colonist, deportee, disloyal, disunify, djibouti, domestic, dominica, drive in, emigrant, emigrate, evacuate, faineant, federate, flanders, friendly, frontier, homeland, homespun, importer, interior, internal, jamaican, longways, mainland, monetize, nasalize, national, occupier, olympiad, olympics, overseas, passport, pastoral, phenicia, populate, probably, re-enter, roadbook, romanian, rumanian, shipping, surround, terrasse, thailand, togolese, williams, windhoek, yugoslav

9 letters:
air force, air power, argentina, barnstorm, benighted, bluegrass, bumpkinly, citizenry, civil war, dirt bike, dreamland, exchanger, exporting, extradite, foreigner, heartland, holy land, immigrant, immigrate, importing, indelibly, intercept, irredenta, irridenta, isolation, liverpool, marchland, mauritian, mercenary, migration, missioner, nashville, nonnative, normalize, originate, outlander, palestine, patriotic, phoenicia, piggyback, playactor, reconquer, red china, rock wren, roosevelt, roumanian, rusticate, scrambler, self-rule, singapore, sovietize, st. lucia, sultanate, tax haven, trade gap, tyrannise, tyrannize, unfocused, upcountry, vicereine

10 letters:
acceptance, aggressive, allegiance, ambassador, assimilate, autostrada, barn dance, borderland, campestral, cape verde, cappadocia, channelize, chatelaine, compatriot, countryman, decimalize, dependency, dreamworld, embassador, emigration, expatriate, expedition, fatherland, glory fern, grand turk, grind down, guillotine, gunrunning, home front, landlocked, mauritania, mauritanie, micronesia, militarize, missionary, monarchial, montenegro, motherland, muritaniya, nationwide, noncitizen, occupation, off-roader, patriotism, population, porto novo, preference, provincial, rededicate, repatriate, rockabilly, rock music, ruritanian, san marino, sweepingly, trail bike, tramontane, treasonist, westernize

11 letters:
addis ababa, afghanistan, barnstormer, cargo ships, christiania, colonialism, countryseat, countrywide, customhouse, deportation, devaluation, exportation, extradition, immigration, importation, inland bill, irredentism, irridentism, langlauffer, lilliputian, mauritanian, nationalism, nationalist, native land, netherlands, never-never, new zealand, north korea, old country, overproduce, panama tree, peripatetic, plainspoken, pretentious, quislingism, recognition, regionalism, rustication, saint lucia, stunt flier, stunt pilot, sufficiency, summer camp, trusteeship, unpatriotic, upper volta, whistlestop, yugoslavian

12 letters:
advantageous, arms control, balkan state, burkina faso, countrywoman, economically, expansionism, expatriation, first strike, foreign-born, foreign bill, guest worker, in-migration, indianapolis, mobilization, monetisation, monetization, partitionist, police state, repatriation, robert frost, sectionalize, shooting box, soviet union, square dance, substantiate, summer house, transmigrate, undocumented, unscrupulous

13 letters:
balkan nation, border patrol, civil liberty, collaboration, country-style, country house, cross-country, cross country, disinvestment, exchange rate, export credit, foreign agent, foreign draft, head of state, import credit, landed estate, money changer, mountain bike, nationalistic, north vietnam, olympic games, out-migration, pony-trekking, promised land, rock-and-roll, rock 'n' roll, rock and roll, state capital, the argentine, trade balance, unpretentious, virginia reel

14 letters:
bahama islands, balkan country, breathing room, brobdingnagian, central africa, chief of state, country doctor, cracker-barrel, defence policy, defense policy, demonetisation, demonetization, infrastructure, longways dance, mainland china, mother country, mountain trail, neocolonialism, neutralisation, neutralization, shooting lodge, spanish guinea, square dancing, states general

15 letters:
afars and issas, banana republic, communist china, defence program, defense program, domestic flight, espionage agent, hillbilly music, merchant marine, monetary system, self-government, the netherlands, three-day event, topographically, truman doctrine, trust territory, visible balance

16 letters:
albanian capital, all-terrain bike, attorney general, balance of trade, border patrolman, british honduras, capital of benin, displaced person, merchant vessels, military control, multiculturalism, never-never land, nigerian capital, rate of exchange, robert lee frost, stateless person

17 letters:
capital of norway, constitutionalize, country of origin, defensive measure, equatorial guinea, farley maidenhair, high commissioner, invisible balance, military governor, political liberty, sterculia apetala

18 letters:
apostolic delegate, capital of indiana, capital of nigeria, franklin roosevelt, hostile expedition, medium of exchange, self-determination, soldier of fortune

19 letters:
balance of payments, antigua and barbuda, barbados maidenhair, capital of ethiopia, dangling participle, diplomatic immunity, estate of the realm, government-in-exile, military expedition, phrynosoma cornutum, st. kitts and nevis, texas horned lizard, trusteeship council

20 letters:
capital of tennessee, cross-country riding, international flight, salpinctes obsoletus

21 letters:
cross-country jumping, foreign correspondent, military intelligence, north american nation, saint kitts and nevis, st. christopher-nevis, systeme international

22 letters:
farley maidenhair fern, north american country

23 letters:
saint christopher-nevis

24 letters:
central african republic

25 letters:
franklin delano roosevelt

26 letters:
people's republic of china

27 letters:
adiantum tenerum farleyense, military-industrial complex

30 letters:
st. vincent and the grenadines, systeme international d'unites

32 letters:
saint vincent and the grenadines

33 letters:
balance of international payments

35 letters:
union of soviet socialist republics