Well, there do exist more or less balanced and moderate parliamentary systems such as West Germany's and by extension today's Germany's political system to the extent that it does not deviate from the old West German Fundamental Statute. I'd like to emphasize the German case, because it combines federalism (another crucial check and balance) like the United States. Also, the English Westminster SYstem in its better days, not only because of England's and the United States's cultural and historical similarities, but more because it used to incorporate another check and balance that exists and should continue to exist in the United States, the single-member, winner-take-all constituency. Both England and Germany have large conservative parties that operate under the adversarial, disciplined way I describe, especially in England.
And then there are the much more common basket case parliamentary countries like Spain, or Italy or Israel, or the Fourth French Republic, and Belgium and the Netherlands and all the Latin American countries which have been foolish enough to incorporate parliamentary features into their political systems such as Perú (and which have paid dearly for such mistakes). Unlike the United States, these countries have fewer (or in the case of Israel, zero) checks and balances on whoever happens to be in government at the time. Of course, the unlimited and unconstrained majoritarian democratism of parliamentary systems is not by itself enough to produce weimarization nor turn the system into what Lord Hailsham very accurately described as an elective dictatorship.
The danger comes when the political parties begin functioning like I described the Republican Party to behave. The tendency is for the party to become, in effect, a vehicle for the idiosyncrasies of its leader. And this happens because, like Mr. Trump does, party leaders either select candidates for everything (or has great influence on the selection) leading to the institution being filled by sycophantic yes-men (backbenchers, that is). That, combined with the essentially unconstrained power of a parliamentary majority can make a parliamentary democracy, metaphorically speaking, an elected dictatorship (rule by the party that has a majority which in turn is controlled by the party leader and Prime MInister). And the inherent instability of some parliamentary systems (like Israels, infamously chaotic) means that "one" elected dictator can be replaced by another, either when some razor-thin majority changes or when a "Frankenstein" coalition government suddenly collapses, with the inevitable huge swings in politics (political chaos, or in other words, Weimarization).
