Is the two party system to blame for Trump having such a high approval rating?

[Cashew]

Yes, Trump would be nearly universally reviled if conservatives had another viable party to vote for.

[Hydera]

Well in France with a two round system. Hollande got 28.6% of the first round but his approval was at 5-10% for his last two years. Which meant his first round vote wasnt his floor.

If anything its not the two party system but the political dynamics(tldr: demographics)which allows him to have a 39% approval. Each side is a combination of groups that do not like the opposite side for many reasons. And except for scandal like watergate or recession like in 08. Presidents will still manage to have sizable support over 30%.

[Hammy]

Partially. There are many "my party, right or wrong" who will blindly go with them because they don't want to indirectly approve of the other side. At the same time, I think that's a small number at this point and that most of Trump's approval are people who genuinely support him (which is a bit terrifying to think about.)

[Antonio the Sixth]

Partly, in that it's one of the features of the American political system that have led to the extreme political polarization we see today. But I'm more interested in the features of American social life that make it possible.