What is the difference between national highway and international highway give one example of each

As the terms indicate, a national highway is contained within a country and an international highway joins two or more countries, but the "international" designation is not accurate. Each nation takes responsibility for highways within its own borders, and has no jurisdiction over the road once it crosses the border.
In the United States, prior to the 1950s, numerous highways were part of the U.S. numbered highway system; these ran through several states but kept the same number. An example is U.S. Route 101, which extends along the West Coast. Individual states or localities are largely responsible for their maintenance. These routes use black-and-white signs.
During the presidential administration of Dwight D. Eisenhower, the Insterstate Highway System was created with the Federal-Aid Highway Act of 1956. New, four-lane, divided highways were constructed. Some of these routes run coast to coast, such as I-80 from San Francisco to New York. The federal government is largely responsible for these highways. They are marked by red-white-and-blue signs, and the number includes an “I.”
One international highway system connects Canada, the United States, and Mexico. Often abbreviated as “CANAMEX,” it applies to several routes. Within the United States, the portions corresponding to the CANAMEX Trade Corridor were established in 1995.
https://web.archive.org/web/20080110203215/http://www.canamex.org/fed_def.asp

A national highway runs through a particular country, often across several states or provinces. An international highway runs through more than one country and runs across the border of at least two different countries. In the U.S., examples of national highways include I-15, U.S. 66 (the infamous Route 66), U.S. 80, and many more. U.S. 20 runs from coast to coast and is one of the longest national highways. An example of a national highway in Britain is the M3. 
A well-known international highway is the Pan American Highway, which runs through the North America and much of South America. The Karakoran highway, 800,000 miles in length, runs from China to Pakistan. In Europe, international highways are designated with an E, followed by a number, such as E18 or E99. In Europe, international highways running north to south have odd numbers. Those running east to west or vice versa have even numbers.
https://www.roadtraffic-technology.com/projects/international-e-road-network/