Apologies to the United States from California. Per the National Weather Service smoke from our fires has reached the east coast. HOW?

The majority of the mainland US is located between 30 and 60 degrees (north or south) latitude.  Withing this range, the airflow is from west to east.  We call these the "prevailing westerlies".  Anything withing this area (storms, smoke, volcanic ash, radiation, etc.) will generally move from the west to the east as well (local anomalies notwithstanding). 
Below 30 degrees, the winds (airflow) moves from east to west - called the "trade winds".  This is why many hurricanes generally move from east to west while most frontal systems generally move west to east.

Fun fact: As smoke from california fires continues to head east it will, eventually, circumnavigate the globe - and be right back to california where they originated.  However, as the smoke continues its journey eastward out over the atlantic and beyond, the smoke particles will get more and more dispersed.  So when they finally do get back to california they wont be perceptible to the human eye.  Some of the lighter smoke particles will get drawn higher up into the upper atmosphere where they will make this global journey numerous times (years).

Smoke: the gift that keeps on giving -  Smoke particles make good nuclei for H2O vapor to condense around.  Thus eh center of every drop od rain contains a nucleus consisting of dust, smoke or the such.  Therefore, some of the rain and snow that falls this winter (over the northern hemisphere) may contain a trace of smoke from the California wildfires.  Possibly the rain/snow for several years to come will contain some of it as well.