Any group can be victims of racism
Racism a form of prejudice that manifests through a belief in a racial hierarchy. Which groups sit at atop this hierarchy, and which at the bottom, is irrelevant. The dictionary definition of "racism" is "“prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one’s own race is superior.” White people - like any group - can be victims of racism.
Current discussions of racism hold that the dynamics of power in society are a significant factor. However, this factor has no bearing on the essence of racism, as it is the act of discriminating against a member of a different race based on beliefs of superiority. One does not necessarily need to be in a position of power to discriminate or hold a prejudice against someone. In turn, a group's position in the hierarchy of power does not matter. An engagement between John Dennis, a congressional challenger to Nancy Pelosi, and Stefan Goldstone, a protester, demonstrates that someone does not need to be in a position of power to discriminate against another person. John Dennis is a white man, and Stefan Goldstone is a Hispanic man. When the protester was approached by Dennis to engage in civil discourse, the protester grew hostile towards him, the implication being that the protester reacted this way based on Dennis' appearance.  In this case, the protester is not in a position of power since he is the one fighting to affect change. John Dennis, on the other hand, is running to become the congressman of San Francisco. If anyone is in the position of power, it is John Dennis since he is in a better position to affect change. Despite this dynamic, John Dennis was still a victim of discrimination. Even if one was to consider power dynamics as part of this discussion, racism against not only white people but other races still exist. As well-intentioned as it may be, affirmative action programs are a good example. Affirmative action policies are responsible for favoring members of racial groups that are known for having faced discrimination. Showing this kind of preference, however, is a form of discrimination in and of itself. Robert Clegg, the president of the conservative Center for Equal Opportunity, states that where the civil rights laws try to include all races, affirmative action policies only work towards alienating other racial groups, such as white Americans and Asian Americans.  Despite trying to combat systemic racism, affirmative action programs still make a person's race an influential factor in determining their eligibility. The only thing that changes is which race garners preference over another.
Assuming that racism and racial prejudice are distinct from one another, the dynamics of power in society would play a larger role. The defining factor that would make racism different from racial prejudice is one's ability to enforce these beliefs. Racial prejudices are a directed set of beliefs favoring one race over the other, often leading to hurtful behavior. Be that as it may, racism takes it a step further and considers those prejudices when making decisions, disadvantaging racial groups deemed inferior.  Effectively and intentionally hobbling another racial group in society takes having a higher standing in that society's system. In short, the dynamics of power or the existence of a racial hierarchy could play a more significant role when it comes to the inner workings of racism.