While the idea that every vote is equal is a central tenement to the United States sense of democracy, it is clearly not true for US voting systems. The US operates as a representative democracy with voting power given to groups rather than to individuals. The most prominent groups are the 50 recognized US states, which in turn have their own levels of government.
The House of Representatives is distributed based on the population of States which is re-evaluated every census. This affects the number of Electoral votes a State receives to cast in Presidential Elections. Each state is given an electoral vote for each Senator(always 2) plus the number of House Representatives, which they cast for the candidate of choice based on the majority vote in that state.
This means that representative votes are not equal among states and subject to change on a decadal basis. States with very low populations will always recieve at least 3 electoral votes giving them greater proportional power based on population.
The graph below shows the US States, plus Puerto Rico and D.C., with their size by different representation metrics. The size of the circle corresponds to the population per electoral votes. Small circles represent states with less people per electoral vote. These are all states that would have less electoral votes if they were distributed soley on population.
A notable stand out is
Puerto Rico
which recieves 1 House Representative, but that representative has no voting power. Peurto Rico also receives 0 electoral votes even though its population is greater than 21 other States and D.C., which recieves 3 electoral votes.
Electoral and House votes are distributed based on census results, but a lot can change within ten years. The below map shows how populations have changed by state since the last census. Again, a notable stand out is Peurto Rico, which saw its population drop by the highest percentage by far.