ReactJS navbar will not load 100%

I am trying to add a navbar to my ReactJS website and I am trying to add a navbar to my website.
It need the navbar to be on 100% width. I tried using 'width: 100%;'. But it will not make the header 100% .
Here is my Code:

ReactJS:

import React from 'react';

import './Header.css';

function Header() {
    return (
        <nav className="header">
            <a href="#">Home</a>
            <p>   </p>
            <a href="#">About</a>
            <p>   </p>
            <a href="#">Projects</a>
            <p>   </p>
            <a href="#">Resume</a>
       </nav>
    )
}

export default Header;

CSS:

.header > a {
  background-color: #171A25;
  text-decoration: none;
  color: white;
  text-align: center;
  word-spacing: 33px;
}
.header {
    background-color: #171A25;
    align-items: center;
    word-spacing: 33px;
    padding: 1em 1.5em;
}