Agreed, in fact, I'm not sure if "isolationism" would even be relevant to the discussion of big government/small government except in that less foreign intervention would mean less use of government resources.
Before Iraq, wars were things the Democrats always got into for the most part, Vietnam, Korea and so on. And Gulf War I conceivably was justified but I remember Conservatives who certainly didn't want to even go to that.
Conservatives should support smart policies and not get trapped into formulas where "Okay, we're always isolationists" or "Okay, let's kill them off, take their land, and go their for vacation (for no reason)".
There is nothing wrong with supporting Ukraine with better weapons and economic help to keep them from collapsing, and I'll give a good reason why: the Russkies are apparently already talking about doing this to Latvia (a small NATO country) using the whole "separatist" angle. Latvia has a large Russian population, although the majority do not support separatism (though the Russians are already putting out anti-Latvian propaganda). Ukraine did not have a majority of Pro-separatists either. It had only a minority within a minority in the East and South, and the only place where it closed in on having a large population of separatist support was in Crimea. Yet, obviously, this did not stop Russia from lying their butts off and invading Ukraine under the cover of a rebellion.
This is why Russia must be stopped here and now, otherwise it will just keep on happening, and this with the potential of destroying the NATO alliance if the United States does not act when Russia begins testing us in NATO countries using the same strategy.
The dissolution of NATO has been a primary Russian objective since the cold war. If the West is divided against a united totalitarian bloc headed by Russia, we are doomed.