No, most protestants are not required to tithe. I am a protestant, and I have never had to submit proof of my salary. If I were, I'd probably leave whatever church that asked that of me. If I fail to meet a full 10%, then, well, nothing really happens. The sin, if it's even called that, is simply not giving, which most would say isn't even really a sin. I've never been turned away from a church on account of my failure to tithe, and again, if I ever hear of anybody turned away on account of their refusal to tithe, I'd probably leave that church, as they're completely missing the point of grace. I've never been asked to come into a meeting to discuss my financial circumstances, (I'd leave that church, etc. etc.)
That being said, there is sometimes some level of social pressure applied. In some churches, not giving can lead some people to think you're not "committed" enough to the cause of what's happening, which, in itself, is often an implied sin. Implying such a thing isn't really a Biblically correct way to handle things, as the Bible says in 2 Corinthians 9:7:
Each one must give as he has decided in his heart, not reluctantly or
under compulsion, for God loves a cheerful giver.
I don't believe this implication is necessarily conscious, as I think many people are so wrapped up in what they're doing, that they fail to see what it is that God has done for them, and wants to do in them. Of course, you're going to find this in any denomination, Protestant or Catholic.
The proper motivation for a Protestant (or any Christian for that matter) to give to his or her church is simply that they are excited about the message of the Gospel, and they wish to support those whose job it is to share the good news, in the hopes that more may come to know it. In the end, we know that God forgives even those who might have been called to give, but didn't, on account of Christ's sacrifice, so even our giving or failure to give is covered by the blood of Christ.
I will say, anecdotally, that when I do not give, my finances for that month tend to be more constrictive than months when I do tithe. An argument can be made over whether this is because God has blessed me and my family when we give, or whether my finances are in better order simply because I view them more as a stewardship of what God has given me, and so I'm more careful with my spending, but in either case, there seems to be a correlation between "financial peace" and my giving to the church.