The Earth's magnetic force is very weak compared to many of the things around you.
Think of how a child's magnet can overpower the Earth's magnetic field in influencing a compass.
Then think of how much stronger things like electromagnets are that pick up cars not to mention the incredible strength of magnets in brain scanners.
However the Earth's magnetic field does play a big part in shielding us from solar radiation so if the Earths magnetic field does switch we are likely to be 50 years or so without much shielding and that would affect our technology and increase our radiation exposure.