In general, US citizens and resident aliens must file tax returns to the United States on their worldwide income, unless their income does not reach the filing threshold. In your case, even if your income does not reach the filing threshold, as long as you have a Social Security Number, you will want to file to receive the stimulus payment that was issued.
In general, scholarship "income" is not taxable nor reportable when used for qualified education expenses (typically tuition, applicable fees and required materials) towards an accredited college or university. Guidance as to whether or not the university you are attending being accredited can be found here. Scholarship above and beyond those necessary education expenses can be considered taxable in the United States.
However, since the United States treats such income as a type of wage income (although technically not earned income), there are two types of provisions that would likely make any "taxable" amounts not taxable. First of all, any reportable scholarship under $12,550 would be reduced to $0 for the standard tax deduction for a single filer. And if you have taxable scholarship income above $12,550, you still could qualify for the Foreign Income Exclusion because you have not spent 30 days in the last 365 days in the United States. But if you have over $12550 of taxable scholarship (the amount of scholarship spent on nonqualified expenses), then you have a filing requirement in the United States even if you can exempt the income. And, as mentioned above, if you have not received a stimulus check from last year, you will want to file your return to receive that payment.