So don't kick countries into America's jaws where it can turn them into vassals, obviously. When America suppresses them, we boost them. That is how America loses vassals... now, today. Will they come back to cooperate with the US in the future? Maybe, but with a stronger vassal state and weaker lord state, the dynamic will favor the vassal so the American lord cannot get as many concessions. And if we win enough today, the lord may be too crippled to lord for much longer into the future and he may totally lose control of his vassals, leaving him on his last legs.