Can I refuse an American tourist visa if I have a Canadian study visa?

There is a certain chance of refusing a tourist visa in the United States. No matter how good your information is, you may refuse the visa. But as you said, you already have a study visa in Canada. After going to Canada, it is very helpful to study there and apply for a tourist visa in the United States.

However, as mentioned above, no matter how good the information is, there is always the possibility of rejection. Just because you have been to Canada does not mean that your American visa will definitely pass. In fact, whether Canada or the United States, as long as you can prove to the visa officer that you will definitely come back after going to the United States, you will get a visa.