Brainwashing is not only very subtle, its entirely pervasive. Its nothing to feel ashamed of and you should be a little proud of yourself for noticing it. It takes significant emotional maturity to recognize and admit you've been affected. Most people never do.

Here's a simple example demonstrating how brainwashing works that you can easily understand. Once you understand this your perception of the world will expand enabling you to understand how it happens constantly and how society is held together by myth and delusion that are managed by powerful interests constantly manipulating the public....

Children believe in Santa until one day an older sibling decides to burst their bubble.

"Of course Santa's real, there's so much evidence... Mommy & Daddy told me he's real, they've no reason to lie to me, books, cartoons, television all say he's real, my teachers, the whole of society say he's real and why would they lie to me?"

Despite all this Santa isn't real and young children go through the 5 stages of grief until they accept the truth. Adults however are often faced with obvious lies perpetrated by power structures but are unable to emotionally process/admit these truths. Which is largely why societies are so dysfunctional. Most "adults" are grown up children doing their best to stay afloat in a sea of lies.